Multi-channel imaging systems, such as the systems disclosed in U.S. Pat. No. 6,211,955 (the disclosure and drawings of which are specifically incorporated herein by reference) can be used to acquire multi-spectral images of an object (such as a cell). Such systems often have some amount of spectral crosstalk (leakage) across different spectral channels, particularly where there is some mismatch between the spectral widths of each channel (an exemplary channel might span 50 nm) and the spectral emission of fluorescent dyes (an exemplary spectral emission might have a peak spanning about 50 nm and a tail extending for up to another 100 nm) used to tag the cells. In order to obtain accurate spectral data in each channel, it is necessary to compensate the data for this leakage. When dealing with image data, proper compensation requires that the images in the different channels be registered to sub-pixel precision before the compensation routine can be applied. U.S. Pat. No. 7,079,708 (the disclosure and drawings of which are specifically incorporated herein by reference) describes a method to accomplish crosstalk reduction in a system where the multi-spectral images are acquired from the same imaging region. That reference discloses a method to pre-compute X and Y spatial offsets and spectral leakage coefficients between different channels on a multi-channel instrument, which can then be applied to acquired data to accurately align and spectrally compensate the images of the object in each channel. The method disclosed therein supposes that the spatial offsets between channels are a function of the instrument setup, an assumption that is valid for an imaging system where all the image data is acquired from the same imaging region. This type of spatial offset can be considered to be a static spatial offset, because unless the instrument set up is modified (i.e., the alignments of the optical components are changed or the detector is replaced), once computed the spatial offsets will remain unchanged.
However, applicants have discovered that when image data is acquired from two spatially distinct imaging regions at different times (where the two imaging regions are spaced apart along an axis of motion between the imaging system and the object being imaged), there may exist a spatial offset between images acquired in the first imaging region and images acquired at a later time in the second region, where the cross region spatial offset is a function of an error in an estimated speed of the object as it moves between the two different locations. Significantly, because the cross region spatial offset is not a function of the parameters of the imaging system, but rather a function of the speed of the object being imaged, the spatial offset correction technique disclosed in U.S. Pat. No. 7,079,708 cannot correct for the cross region spatial offset. Left uncorrected, the cross region spatial offset degrades the quality of the data collected. This cross region spatial offset can be considered to be a dynamic spatial offset, because the offset can change from object to object, as different objects may be moving at different speeds.
It would be desirable to provide techniques for correcting for cross region spatial offsets between images acquired from spatially separated imaging regions, where such offsets are directly related to an error in an estimated speed of the object as it moves between the two spatially separated imaging regions.